Global navigational satellite systems (GNSS) include the global positioning system (GPS) and the Russian global orbiting navigational satellite system (GLONASS). GNSS-based navigational systems can allow for integration of positioning and navigational capabilities in a variety of civilian and military applications. For instance, in the GPS navigational system, GPS receivers can receive satellite positioning signals from a set of up to 32 satellites deployed in 12-hour orbits around the earth and dispersed in six orbital planes at an altitude of 10,900 nautical miles. GPS satellites can continuously transmit spread spectrum L-band signals, such as a L1 signal having a center frequency of 1575.42 MHz, a L2 signal having a center frequency of 1227.6 MHz, and a L5 signal having a center frequency of 1176.45 MHz. While in civilian applications GPS receivers usually make use of L1 signals, in military applications the GPS receivers can use L1 signals, L2 signals, and/or L5 signals.
A GPS receiver can decode information embedded in received GPS signals and use the decoded information to determine its location. In military applications, GPS signals (or more generally GNSS signals) can undergo jamming. For instance, in a battle field or a war zone, one entity can transmit jamming signals at the L1 center frequency, L2 center frequency, and/or L5 center frequency. Such jamming can prevent GPS receivers from receiving GPS signals transmitted by satellites. The jamming may substantially degrade the signal-to-noise ratio (SNR) of received GPS signals, such that any decoding of information embedded in received signals becomes unreliable.
In order to overcome the effect of jamming, GPS receivers used for military applications may employ anti-jamming techniques. However, as jamming techniques become more sophisticated, implementing anti jamming techniques in GPS receivers can lead to increased hardware and/or software complexity of such GPS receivers. Therefore, new ways to implement anti jamming while reducing complexity and/or GPS receiver dimensions would be beneficial.